lib/libc/stdlib/tfind.c

   1 /*      $NetBSD: tfind.c,v 1.7 2012/06/25 22:32:45 abs Exp $    */
   2
   3 /*
   4  * Tree search generalized from Knuth (6.2.2) Algorithm T just like
   5  * the AT&T man page says.
   6  *
   7  * The node_t structure is for internal use only, lint doesn't grok it.
   8  *
   9  * Written by reading the System V Interface Definition, not the code.
  10  *
  11  * Totally public domain.
  12  */
  13
  14 #include <sys/cdefs.h>
  15 #if defined(LIBC_SCCS) && !defined(lint)
  16 __RCSID("$NetBSD: tfind.c,v 1.7 2012/06/25 22:32:45 abs Exp $");
  17 #endif /* LIBC_SCCS and not lint */
  18
  19 #include <assert.h>
  20 #define _SEARCH_PRIVATE
  21 #include <stdlib.h>
  22 #include <search.h>
  23
  24 /* find a node by key "vkey" in tree "vrootp", or return 0 */
  25 void *
  26 tfind(const void *vkey, void * const *vrootp,
  27     int (*compar)(const void *, const void *))
  28 {
  29         node_t * const *rootp = (node_t * const*)vrootp;
  30
  31         _DIAGASSERT(vkey != NULL);
  32         _DIAGASSERT(compar != NULL);
  33
  34         if (rootp == NULL)
  35                 return NULL;
  36
  37         while (*rootp != NULL) {                /* T1: */
  38                 int r;
  39
  40                 if ((r = (*compar)(vkey, (*rootp)->key)) == 0)  /* T2: */
  41                         return *rootp;          /* key found */
  42                 rootp = (r < 0) ?
  43                     &(*rootp)->llink :          /* T3: follow left branch */
  44                     &(*rootp)->rlink;           /* T4: follow right branch */
  45         }
  46         return NULL;
  47 }